Malleable iron casting



Patented Aug. 30, 1932 UNITED STATES PATENT OFFICE RALPH T. R'YCROFT, OF KENMORE, NEW

YORK, ASSIGN OR TO JEWELL STEEL &, MALLE- ABLE (70., OF BUFFALO, NEW YORK, A CORPORATION OF NEW YORK MALLEABLE IRON CASTING No Drawing. Application filed June 20,

This invention relates to malleableized iron castings.

It'has for its principal object the production of a malleableized iron alloy casting Lltt which is especially adapted for use where heat and stress resisting qualities are important requirements.

The invention contemplates the addition of a suitable quantity of chromium and nickel to a molten iron mixture, the production of the castings in the usual manner, and an annealin treatment which renders the casting malleable. The chromium and nickel impart the heat resisting quality while the nickel also acts as a retarding agent-to prevent the casting from becoming too hard as a result of the addition of the chromium. I have discovered that the chromium and nickel in the malleableized casting also arrest grain growth and thereby insure the production of castings having a very close grain, by virtue of which the castings are capable of retaining their shape under high temperatures.

In the production of castings in accordance with the invention, I add nickel and chromium to iron, either in the molten state or with the charge, the mixture being high enough in combined carbon and low enough in graphitic carbon to produce a casting which will show a white fracture when broken instead of a gray fracture. The percentages by weight of nickel and chromium are determined with reference to the require ments of use. For example, in the production of locomotive grate bars, I preferably add 1% of nickel and of chromium, it being understood, of course, that the proportions may be varied within certain limits depending upon the use to which the particular castings are to be put. Locomotive grate bars cast from the foregoing composition and prepared in accordance with the invention although approximately fifty per cent less in weight than ordinary gray iron locomotive grate bars have uniformly had a long life and have uniformly resisted the high tempertaure to which they are subject.

Where resistance to tensile stresses is an important requirement the iron should have a relatively low or minimum percentage of 1929. Serial No. 372,535.

carbon since the degree of elasticity is less as the percentage of carbon is greater. In such cases, therefore, locomotive grate bars being an example, I employ iron having a percentage ofcarbon substantially less than that of the iron employed in the ordinary or standard practice prevailing in the majority of malleable foundries and obtain castings having a very high elastic limit and high wear resisting qualities. For example for this purpose I preferably employ base iron having carbon not substantially in excess of 2.35 per cent Whereas in the majority of malleable foundries the base iron has 2.50 per cent or more of carbon.

The nickel and chromium which are added to the molten mass may be in the form of shot or powder. When the added nickel and chromium have been assimilated the alloy is cast in the forms desired. The castings are then removed from the molds at temperatures ranging from 600 F. to 900? F. and depending on the requirements of instances preferably placed in cooling ovens Where they are quickly heated to a tempera ture of about 1300 F. after which they are slowly permitted to cool to room temperature, this treatment being for the purpose of eliminating casting strains.

After the castings have been removed from the cooling ovens, they are packed in annealing ovens where their temperatures are raised to from 1550 F. to 1850 1:. within from 12 to hours. This temperature 18 maintained from 425 to hours and then the castings are permitted to cool slowly for about 50 hours to 900 F. the ovens are opened and. the castings exposed to air supplied by any suitable means such as a fan, and further cooled, the castings then being ready for use.

Having fully described my invention, I claim:'

1. A malleableized iron alloy casting having the qualities specified and containing car- 9 bon up to and including substantially 2.35 per cent, substantially l per cent nickel and substantially per cent chromium.

2. A locomotive grate bar consisting of a use are in some At the expiration of this time,

malleableized iron alloy casting having the qualities specified and containing carbon up to and including substantially 2.35 per cent, substantially 1 per cent nickel and substantially per cent chromium.

In testimony whereof I aflix my signature.

RALPH T. RYCROFT. 

